Explosive assembly and method of making it



Feb. 13, 1951 c. H. CAREY ETAL EXPLOSIVE ASSEMBLY AND METHOD OF MAKINGIT Filed May 20, 1944 Claude H Carey Donald R. Wallon INVENTORS WATTORNEY Patented Feb. 13, 1951 UNITED EXPLOSIVE ASSEMBLY AND METHOD OFMAKING IT Clande.-'H."Oarey, Wilmington, Del., and Donald R. Walton,

tion ot Delaware Tamaqua, Pa., assignors to Atlas Powder Company,Wilmington,

Del., a corporamuse... May 20, 1944, Serial No. 536,488

Claims.

of loading.

A still further object of the invention is to provide an improvedexplosive assembly permitting the use of different apparent densities ofexplosive-in the same assembly.

Another object of the invention is the provision of an improvedexplosive assembly containing an explosive having a higher overallapparent density.

Still another object of the invention is the provision of an explosiveassembly containing explosives under difierent states orcompressibility.

A further object of the invention is the provision of an explosiveassembly with improved control of apparent density during manufacture.

A still further object of the invention is the provision of an improvedexplosive assembly containing ammonium nitrate explosive.

Other objects will be apparent from the following description.

As the apparent density of most explosive compositions is increased, asby hard packing. there is a reduction in sensivity to detonation and adecrease in' propagation sensitivity. This phenbmenon is particularypronounced withexplosives containing a high proportion of ammoniumnitrate and no, or but a. small proportion, of, nitro glycerine. It isto explosives of this type to which the present invention is principallydirected. a

The term "density as used in the present specification and claims, inconnection with explosive compositions, refers to apparent density,which may be altered by packing.

In most blasting operations, it is desirable fromthe economic point ofview, that the explosive charge in a cartridge be as dense as possibleand yet be sufficiently sensitive to detonation and propagation in abore hole. With a dense explosive, a smaller diameter bore hole'may beemployed for the same weight of explosive than is required for a lessdense explosive. Furthermore, it is required in some blasting operationsthat the explosive charge be concentrated into as small a space as ispossible in order to secure the proper "tamed by the use of a highdensity explosive.

Also, where muddy water of high specific gravity exists in a bore hole,a dense explosive charge sinks more easily and more rapidly to thebottom. Furthermore, greater economy of manufacture is brought aboutbythe use of smaller explosive assemblies with dense explosivecompositions, as compared with the larger assemblies which are necessarywhen explosives of less density are used.

Usually the density of the explosive charge in an assembly is controlledby the amount of pressure exerted on the charge in packing the assembly;customarily, the charge is added to the assembly container in incrementsduring the'packing operation and packed down either mechanically or byhand with packing sticks. The greater the pressure during packing, themore the density of the finished cartridge and the more rigid and harderthe cartridge becomes.

When the explosive is packed in thin sheet metal cans provided withroiled or locked seams, there are decided advantages derived from hardpacked, and hence relatively incompressible, explosive charges. Inhandling there is less likelihood that the can will be deformed ordented by rough treatment. Deformation or denting, in addition toadversely afiecting the shape of the can, often impairs the waterresistance of the assembly. Also, it is found that a densely packedassembly has improved water resistance of itself when placed in boreholes containing a head of water. The hard packed explosive compositionsaid in preventing deformation of the assembly container by waterpressure.

It is often required that explosive assemblies be resistant todetonation when struck by bullets at high vlocity. Hard packed explosivecompositions are usually more resistant to such detonation than arecompositions of less density.

While a high density of packing for explosive assemblies is desirablefor the reasons stated low sensitivity produced by compression to highdensities. The diilicult initiation of explosive assemblies in which theexplosive is packed under high compression arises not only because ofthe inherent insensitivity of dense hard packed explosive but alsobecause of the fact that hard packed explosive not being readily furthercompressible supports the assembly walls making it difficult for theinitiating force from a detonating element to break through the assemblywalls. Conversely, assemblies containing less highly packed, and hencemore compressible explosive, not only are inherently more sensitive-butalso readily permit the force of initiation-to break through theassembly walls.

effect of the blast. Such an eil'ect must be ob- 00 The presentinvention provides a means where- 3 by a cartridge containing a denselypacked, or relatively incompressible explosive may also include a moreloosely packed, or more compressible J booster charge of consequentlygreater sensitivity.

, placed an explosive in a condition of high compressibility andsufliciently sensitive to be'initiated/ by a commercial detonator. Inthe remainder ot the explosive assembly is placed an explo siyrkih acondition of lower compressibility.

In an assembly prepared according to the present invention, a detonatingelement may be used adjacent the more highly compressible boosterportion of the cartridge, and the booster charge will sufficientlyinitiate the less highly compressible principal, or base, charge.

A specific embodiment of the invention will be particularly described inconnection with the drawing in which:

Figure 1 represents a sheet from which is prepared 'a conical partitionto separate the less highly compressible from the more high compressibleexplosive;

Figure 2 shows the partition finally prepared in the form of a cone;

Figure 3 is a view illustrating a holder for the partition duringpacking and insertion of the partition into the assembly;

Figure 4 is a view of a finished assembly; and

Figure 5 is an isometric view of a modified finished assembly.

Referring to Figure 1, isa fiat cardboard sheet in generally circularform having a radius equal to the desired slant height of the conicalpartition. A segment |2, defined by edges I3 and 14, is cut from sheetEdge I3 is in the form of a flap for insertion under edge M to form coneI5 (Fig.2). Cone I5 is held together by adhesive strip I6 placed overedge I4. Segment I2 is of such size that the circular base of cone l5will fit snugly in cylindrical can 2| (Fig.4). Fig. 3 shows a holder I!provided with a long support l8, which stands up in a base |9 but isremovable therefrom.

To prepare the assembly, cone I5 is placed in a recess provided inholder IT. The charge of booster explosive is packed into the cone to a.desired cap sensitive density. Cylindrical can 2| .(Fig. 4) having oneend open and the other end closed by circular end wall 22 is slippedover holder I1 until end wall 22 rests on cone l5. Then holder l1,bearing packed cone l5 and can 2|, is lifted by means of support I8,which should be of sufficient length for the purpose, and can 2| isinverted and supported so that end wall 22 is at the bottom and cone |5rests thereon. Holder I! is then withdrawn from can 2| and the remainderof the cartridge packed with explosive to the density desired in thefinal car tridge. This density is usually .considerably higher than thedensity of the explosive in cone l5 and requires greater compressionduring packing. Consequently, the base explosive having been packedharder than the booster explosive is less compressible than is thebooster explosive. The open end of can 2| is then sealed and theexplosive assembly shown in Fig. 4 is thereb completed.

In use, a detonating element such as a blastin cap or detonating fuse isfixed to end wall 22 oi can 2| and the booster charge initiatedtherewith. The booster charge initiates the remainder of the explosivein can 2|.

Fig. 5 shows a modification of the assembly. In Fig. 5 the can is showninverted relative to its position in Fig. 4. The modification shown inFig. 5 is similar to that shown in Fig. 4 except that the end wall 22 ofcan 2| is provided with a well 23 for insertion of a detonating element.A tunnel plate lying parailel to and against the end wall of thecartridge and adjacent the booster charge-may also be used for thispurpose.

It is evident that the present" assembly provides a means whereby thesame cartridge may contain explosives of different densities anddifferent compressibilities. The shape of the partition separating thebooster and base charges offers great resistance to deformation byextemah, vertical pressure. Particularly is this true when the peripheryof the partition is laterally supported. Since the partition isresistant to deformation, a low density or highly compressible explosivemay be maintained in the partition even though explosive is packed tohigh density or less compressible condition on the other side of it.This is particularly important in the case of granular explosives havingfree flowing characterlstics. Granular explosives are usually quitedesirable for explosive assemblies of the present type for the reasonthat they permit uniform densities throughout their bodies. Uniformdensity is, of course, desirable to obtain uniform sensitivitythroughout the charge.

It has been found that during the packing of partitions of the type ofthe present invention the shape of the partition has the importantproperty of preventing the development of unduly high density in thebooster charges. The explosive flows along the sides of the partition sothat vertical packing force produced by packing sticks is dissipatedinto parts of the volume defined by the partition which are not directlyaffected by the packing pressure, and excess of packing pressure causesa flow of explosive upwards along the sloping partition. This actionprevents unduly hard packing. The use of partitions according tothepresent invention results, therefore, in more uniform densitiesinside each booster charge and among a series of booster chargesirrespective of ordinary variation in pressure exerted by packingsticks. This uniformity in density makes for desirable uniformity ofsensitivity of detonation.

The separating partition may be made of metal, heavy paper, cardboard,plastic or other rigid materials, as also may be the external cartridge.The separating partition is preferably made in the form of a cone,though it may also be made in the form of a pyramid, or of a truncatedcone or pyramid, or of a hemisphere, or in any form the cross-sectionalarea of which diminishes, proceeding away from the base. It ispreferredthat the partition be laterally supported at its base; thoughserviceable cartridges may be prepared I even though this is not done.When a cone is to If a rectangular cartridge is employed, a pyra- -midis. the best partition to obtain this effect.

However, since a cone is easy to make and gives great resistance todeformation, it is usually preferred that cylindrical assemblies withcones be employed.

When a cone is employed, the height of the cone depends upon thediameter of the cartridge and the apex angle of the cone. As the apexangle of the cone is unduly increased the resistance of the cone tocompression undesirably decreases. Apex angles as high as 120 may beused, however, with entirely satisfactory results, and greater anglesmay be used with somewhat less protective effect.

On the other hand, as the apex angle of the cone is unduly decreased,the tendency of the walls to make the explosive flow outwardly underexcessive packing pressures is undesirably reduced. Apex angles as lowas 60 may be used satisfactorily and smaller angles may be used withsomewhat less advantage.

An apex angle of about 90 has usually been found to be about optimum.

The invention has been found eminently satisfactory using an 8% in.diameter sheet metal cartridge 17% in. in length having a cone 8 in. indiameter at the base, 4 in. high, made from 8-ply cardboard faced on oneside.

The present invention provides a definite advantage in that the amountof booster charge employed may be made quite small for the reason that alarge area is provided upon which a detonating element may be aflixed;and, at the same time, the boosting charge has considerable depth.

The booster charge and the base charge may be made of the samecompositions, the increase in sensitivity necessary to the booster beingobtained only by the decrease in density. On the other hand, the boostercharge may be made of a different composition than the base chargeincluding, for example, larger quantities of sensitizer, or sensitizersproducing more highly sensitive charges.

For some applications, it has been found desirable to include asensitizer and relatively loose charge in the cone, a charge containingsimilar or somewhat less sensitizer immediately adjacent this cone and acharge containing little sensitizer in the remainder of the assembly.

Explosive charges prepared according to application Serial Number351,211, filed by Claude H. Carey August 3, 1940, now abandoned, areeminently satisfactory for use in cartridges of the present type.

Other modifications of this invention will be readily apparent to thoseskilled in the art.

The expression cap sensitive used in the claims as descriptive ofexplosive compositions is intended to mean a composition which isefficiently initiated by a commercial detonating element such as a fusecap, an electric blasting cap. or a detonating fuse.

What is claimed is:

1. A power producing explosive assembly comprising a rigid cylindricalcontainer having circular end walls, a rigid conical partition having anopen base spanning said container and freely resting against one endwall of said container, said conical'partition extending toward theopposite end of said container, and having an apex angle between about60 and about 120, a booster explosive in said conical partition, a morehighly compressed and less sensitive explosive than said boosterexplosive in the remainder of said container and a receptacle for adetonating element adjacent said booster explosive.

2. A method of preparing an explosive assembly which comprises providinga rigid conical partition having an apex angle between about 60 andabout packing said conical partition with explosive to a desired capsensitive density, inserting said conical partition containing saidexplosive into a rigid cylindrical container with the base of saidpartition against a circular end wall of said container, and with saidpartition extending toward the opposite end of said container, saidcontainer having diameter such that it fits snugly around the base ofsaid conical partition, packing explosive in said container and aroundsaid partition under greater pressure than was employed in packing saidfirst-men-' tioned explosive, and closing said container.

3. A power producing explosive assembly comprising a rigid cylindricalcontainer having circular end walls, a rigid conical partition having anopen base spanning said container and freely resting against one endwall of said container, said conical partition extending toward theopposite end of said container and having an apex angle between about 60and about 120, a booster explosive in said conical partition, and a,more highly compressed and less sensitive explosive than said boosterexplosive in the remainder of said container.

4. A power-producing explosive assembly comprising a rigid cylindricalcontainer having circular end walls, a rigid cardboard conical partitionhaving an open base spanning said container and freely resting againstone end wall of said cotainer, said conical partition extending towardthe opposite end of said container and having an apex angle betweenabout 60 and about 120, a booster explosive in said conical partitionand a more highly compressed and less sensitive explosive than saidbooster explosive in the remainder of said container.

5. A method of preparing an explosive assembly which comprises providinga rigid conical partition having an apex angle between about '60 andabout 120, packing said conical partition with explosive to a desired-cap sensitive density, inserting said conical partition containing saidexplosive into a rigid container with the base of said partition againstan end wall of said container and with said partition extending towardthe opposite end of said container, said container having dimensionssuch that it fits snugly around the base of said conical partition,packing explosive in said container and around said partition undergreater pressure than was employed in packing said first mentionedexplosive, and closing said container.

CLAUDE H. CAREY.

DONALD R. WALTON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 196,767 Rand Nov. 6, 1877 273,156Reed Feb. 27, 1883 939,886 Wolsey et al Nov. 9, 1909 1,406,844 Gelm Feb.14, 1922 1,950,019 Biazzi Mar. 6, 1934 2,075,969 White et a1. Apr. 6.1937 2,129,508 Slusser Sept. 6, 1938 I 2,171,384 Young "-1 Aug. 29, 1939FOREIGN PATENTS Number Country Date 356,064 France Jan. 11, 188'!300,150 Germany Oct. 28, 1919

